Red-eye is a problem commonly encountered in photography when light (typically from the camera's flash) reflects off the retinas at the back of the subject's eyes and causes the subject's eyes to turn red. Red-eye has been a problem for many years, and although a variety of solutions have been proposed to cure the problem, these solutions tend to be costly, cumbersome, and/or ineffective. One such solution is to use a bounce flash so that light hits the subject's eyes from the side (or above/below) rather than straight-on, thereby preventing the reflected light from coming straight back to the camera's lens. Bounce flashes, however, are cumbersome (often rivaling the size of the camera) and costly. Another solution is to pre-flash the subject, thereby causing the subject's pupils to close and decrease the amount of light allowed into the subject's eyes when the picture is taken. These pre-flash solutions, however, are not always effective, and cause a delay (while the pre-flash is operating) before the picture is actually taken during which time the subject may move.
Attempts have also been made to cure the red-eye problem after-the-fact by processing the image to remove the red from the eyes. Computer software packages are available that allow for the removal of red-eye, such as by changing the color of the red portion of the eye. Some systems require manual selection, by the user, of the pixels within the image that are part of the red eyes prior to removing the red-eye. These systems are rather user un-friendly due to the steps the user must follow to identify exactly which pixels are part of the red eyes.
Other systems have attempted to automatically detect where the red-eye portions of an image are (as opposed to other non-eye portions of the image that are red). Such systems typically start by using face detection techniques to determine where any faces are in the image and where eyes are within those faces. Once these faces (and eyes within them) are detected, the systems try to determine whether the eyes are red eyes. These systems, however, can have poor performance under many circumstances (e.g., when a face is partially obscured, such as by heavy shadows or heavy beards, when the face has an unusual expression or is distorted, etc.).
The invention described below addresses these disadvantages, providing improved red-eye detection systems and methods.